﻿    <p>
      A feature element addition is a specialization of the general
      feature element, that represents an existence dependent
      element which modifies the shape and appearance of the
      associated master element. The
      <em>IfcFeatureElementAddition</em> offers the ability to
      handle shape modifiers as semantic objects within the IFC
      object model that add to the shape of the master element.
    </p>
    <p>
      The <em>IfcFeatureElementAddition</em> is associated to its
      master element by virtue of the objectified relationship
      <em>IfcRelProjectsElement</em>. This relationship implies a
      Boolean 'union' operation between the shape of the master
      element and the shape of the addition feature.
    </p>
    <p>
      The local placement for <em>IfcFeatureElementAddition</em> is
      defined in its supertype <em>IfcProduct</em>. It is defined
      by the <em>IfcLocalPlacement</em>, which defines the local
      coordinate system that is referenced by all geometric
      representations. The local placement is always defined in
      relation to the local placement of the element to which the
      feature element is added:
    </p>
    <ul>
      <li>The <em>PlacementRelTo</em> relationship of
      <em>IfcLocalPlacement</em> shall point to the local placement
      of the same <em>IfcElement</em>, which is used in the
      <em>HasAdditionFeature.RelatingElement</em> inverse
      attribute.
      </li>
    </ul>
<blockquote class="history">
HISTORY&nbsp; New entity in IFC2x2.
</blockquote>
<blockquote class="change-ifc2x2">
IFC2x2 CHANGE&nbsp;  The entity is introduced as an upward compatible extension of the IFC2x
platform. It is an intermediate abstract supertype without defining its own explicit attributes.
</blockquote>